Forensic Neuropsychology in Personal Injury Cases II

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Forensic Neuropsychology in Personal Injury Cases
II

• Russell M. Bauer, Ph.D.
• July 17, 2008

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Assessment of Malingering and Poor Effort

• Issues with definition
• Intentional (intention)
• Fabrication or exaggeration (action)
• For purposes of gain (motive)
• Explanatory models (Rogers, 1997)
• Pathological (mental disorder)
• Criminological (fake)
• Adaptational (meeting adversarial demands)
• Cognitive vs. Somatic Malingering

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Diagnosis Threat (Suhr Gunstad, 2002)

• 37 MHI (17 in diagnosis threat condition
• Diagnosis threat told selected because of a MHI
  history a growing number of studies show that
  many individuals with head injury show cognitive
  deficits in neuropsychological tests

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Suhr Gunstad, 2002
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Suhr Gunstad, 2002
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Effort, Motivation, Response Styles
Frederick et al., 2000
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Slick (1999)

• Considers evidence from NP and self report
• NP criteria
• Definite or probable response bias
• Discrepancies/inconsistencies between NP data and
  patterns of brain functioning, collateral
  reports, reports of past functioning

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Slick et al, 1999 (contd)

• DEFINITE MND
• Presence of financial incentive
• Definite negative response bias
• Behaviors that meet criteria for negative
  response bias that are not fully accounted for by
  psychiatric, neurological, or developmental
  factors

• PROBABLE MND
• Presence of financial incentive
• Two or more types of evidence from NP, excluding
  definite response bias, or one piece of evidence
  from NP and one from self-report

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Malingering Research Literature

• Case study
• Simulation studies
• Interpretive issues
• Appropriate designs
• Differential prevalence design
• contrasting high and low baserate groups (e.g.,
  groups with and without financial incentives)
• Valuable mostly for determining average
  performances
• Known-groups design
• Selecting groups on the basis of malingering
  criteria (e.g., Slick, et al)
• Examining differences between the groups

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Selecting Specialized Cognitive Effort Tests

• Ease of use
• Credibility of rationale
• Operating Characteristics
• Incremental validity
• TBI vs. PPCS
• Coaching issues
• There is not likely to be a best test in all
  circumstances

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Commonly Used Specialized Tests

• Portland Digit Recognition
• Digit Memory Test
• Computerized Assessment of Response Bias (CARB)
• Word Memory Test (WMT)
• Victoria Symptom Validity Test
• Test of Memory Malingering
• Validity Indicator Profile
• Rey 15-Item Test
• Dot Counting Test

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Detecting Anomalous Results with Embedded
Measures and Performance Patterns

• Measures within standard NP tests that signify
  noncredible or suspect performance
• Identification of such measures can be rational
  or empirical
• May be less subject to coaching than separate
  measures

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Pattern Analysis

• Pattern Analysis
• With HRNB, DFA outperforms clinicians (80-90 v.
  50-60)
• Most DFAs multivariate , consisting of attention
  and memory measures
• Generally, malingers score better on hard
  measures
• DFAs exist for WMS-R, WMS-III, WAIS-R, WAIS-III
  and other tests
• Before using, investigate whether the DFA was
  validated/cross validated with known groups or
  simulators

Iverson Binder, 2000 Larrabee, 2005
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Embedded Measures Motor, Sensory, and
Perceptual-Motor

• Perceptual-motor pseudoabnormality should not be
  overlooked b/c of emphasis on higher cognitive
  disabilities
• Approaches
• Neurologic exam
• Sensorimotor impairments on NP exam
• Findings
• RCFT copy 50 sensitive with lots of FP
• Malingering groups favor memory over
  visuoconstructive impairment (e.g. memory trials
  of RCFT discriminate better)
• Generally large grip strength effect size in NG
  designs
• Reduced FT speed in the context of MHI

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Embedded Cognitive Measures

• WMS-R/WMS-III
• Malingerers Attention/Concentration lt General
  Memory
• Opposite pattern to typical head injury
• Rarely-missed index on LM delayed recognition
  trials
• WAIS-R/WAIS-III Digit Span
• Malingerers Low digit span performance (ACSS lt
  5)
• Reliable Digit Span (sum of longest correct span
  for both trials lt 8)
• Vocabulary Digit Span (low digit span while
  vocabulary is high)
• CVLT
• Malingerers Low recognition (hits
  forced-choice)
• Cutoff scores for recall trials produce variable
  false-positive rates
• Variable results with most widely used cutoffs
  (Millis et al) Total lt 35, LDCR lt7, delayed
  recognition lt11, discriminability lt 81
  sensitivity in question, not specificity

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Malingering Patterns in N? Tests

• Pattern Analysis
• Word Memory Test
• Malingerers Inconsistent responding, poor
  initial recognition
• Pattern should reflect severity of impairments
• Category Test
• Malingerers Poor performance on first 2 subtests
• Wisconsin Card Sorting Task
• Malingerers Poor ratios of categories completed
  compared to both perseverative errors and failure
  to maintain set

Iverson Binder, 2000 Larrabee, 2005
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Why being a knowledgeable neuropsychologist is
important

• You know likely patterns of impairment
• You know psychometric relationships among tests
• You know course of recovery
• You know about contributory factors (e.g., LD,
  depression, etc.)
• You can compare what you see to what you expect

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Common suspect neuropsychological signs on NP
testing

• Recognition ltlt recall (hits, discriminability)
• Extremely poor DS in the context of normal
  auditory comprehension (RDS)
• Motor slowing (e.g., reduced tapping) relative to
  overt motor disability
• Excessive failures-to-maintain-set on WCST
• Discrepancies between test level and level during
  informal interaction
• Other impossible signs

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Some Take Home Messages

• Use multiple measures (forced choice, embedded,
  etc.)
• Clarify your goals sensitivity, specificity,
  etc.
• Be aware of correlations among malingering
  measures
• Look for emerging research on sensitivity/specific
  ity of multiple indicators

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Symptom Exaggeration

• Self-Report of Symptoms
• May be exaggerated due to other variables
  (depression, pain, stress)
• e.g., Post-Concussive Syndrome persisting for
  more than 3 months
• MMPI-2
• Malingerers tend to show elevations in clinical
  scales 1, 2, 3, 7, and 8, the Fake Bad Scale
  (FBS), VRIN, TRIN, the Infrequency-Psychopathology
  Scale F(p).
• The F Scale and F K does not appear to be as
  sensitive, and therefore valid profiles may be
  obtained.
• Caution should be given to interpreting the
  clinical scales and F Scale derivatives, as these
  can be easily influenced by psychiatric
  comorbidities.

Iverson Binder, 2000 Larrabee, 2005
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Detecting Somatic Malingering

• Symptom report, as well as cognitive performance,
  can be controlled by the litigant
• Use of MMPI-2
• F-scale, F(p)
• VRIN, TRIN
• Subtle-Obvious
• F-K index
• Revised Dissimulation Scales
• These scales may not be sufficiently sensitive to
  TBI-related claims, despite neuro-psychological
  differences

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Lees-Haley FBS

• Model of goal-directed behavior
• Want to appear honest
• Want to appear psychologically normal except for
  the influence of injury
• Avoid admitting longstanding problems
• Minimize pre-existing complaints
• Minimizing pre-injury antisocial or illegal
  behavior
• Presenting plausible injury severity

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Lees-Haley FBS (contd)

• 18 True , 25 False
• Does not correlate very strongly with F-scale
  derivatives
• Most scale items overlap with neurotic side of
  MMPI
• Cut-off mid 20s, with varying false positive
  rates increasing security with scores gt 25-27

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FBS Operating Characteristics

• Most frequently failed indicator of MND
  (Larrabee)
• FBS gt 27 has Sn.46 , Sp.96, better than F or Fb
  (Greve et al)
• Sensitive to symptom exaggeration in personal
  injury, not just litigation
• Cutoffs determine TP, FP rate

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Critical Studies

• Butcher et al (2003)
• Unacceptably high FP of FBS (24 of males, 37.9
  of females exceeded cutoffs)
• Psychiatric, corrections, medical, pain, VA,
  personal injury litigants
• No measures of symptom validity external to the
  MMPI
• No report of who was litigating
• Cant compute specificity or sensitivity without
  this information
• Bury Bagby (2002)
• PTSD vs. students (standard and exaggeration
  instructions)
• F family produced best overall classification
  rates
• Entire PTSD sample were being evaluated for
  workplace disability
• Mean PTSD FBS was 26.31
• No independent measures of malingering or
  exaggeration

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